The present invention relates generally to the field of electrical enclosures, such as enclosures for motor control centers (MCCs) used in industrial and commercial settings. More particularly, embodiments of the present invention relate to systems and methods for grounding the load connections.
A range of applications exist for packaged electrical and electronic components, particularly power electronic components such as those used to power loads in industrial applications. In one type of packaged system, typically referred to as an MCC, various switch gear, control devices, protective circuit devices, programmable logic or automation controllers, motor drives, and so forth are housed in a large enclosure that may be subdivided into compartments, bays, drawers or the like (e.g., sometimes referred to as “buckets”). The enclosure is supplied with power by power buses that extend generally in a plane toward the rear of the enclosure. The individual compartments typically house associated circuitry that may be withdrawn from the enclosure for servicing and replacement. Compartmentalizing such systems greatly enhances the ability to service the system components, and also serves to isolate the system components from one another. Thus, where access or service is required for components within one compartment of the enclosure, that compartment alone may be opened and the component support withdrawn for the necessary service.
Typical MCCs include access to power bus structures at certain locations in the rear section of the enclosure. For example, there may be multiple locations in the rear of the enclosure where compartment supports (e.g., buckets) may be slid into place and plugged into the power buses. Conventional enclosures, for example, may include a dozen rows of slots through which stab contacts extend when the compartments are placed in the enclosure. In some situations, the compartments are withdrawn or disconnected from the enclosures while various equipment (e.g., motors) are still operating. In such situations, even though power is disconnected, the motor may still be creating voltage known as back electro-motive force (EMF). As such, it may be desirable to include a mechanism that grounds the connections of the compartments when they are removed or withdrawn, partially or fully, from the enclosure.